TheParasponia parviflora—Rhizobium symbiosis. Host specificity, growth and nitrogen fixation under various conditions

Abstract

Cross-inoculation experiments withParasponia parviflora plants and a large number of Rhizobium strains isolated from legumes, mainly of temperate origin, showed that strains ofRhizobium trifolii andR. lupini could produce root nodulation in Parasponia. Root nodulation was also obtained with some tropical Rhizobium isolates such as those from Arachis and Albizzia, but not withRhizobium japonicum strains. In addition, strains ofR. leguminosarum, R. phaseoli andR. meliloti produced abnormal root nodules or pseudo-root nodules in Parasponia seedlings. All root nodules induced in Parasponia by foreign Rhizobium species lacked, however, nitrogenase activity. Testing the reverse combination Parasponia-Rhizobium on legumes yielded with regard to root nodulation negative results, except withVigna sinensis and twoMacroptilium species (M. atropurpureum andM. lathyroides). The root nodules produced in the latter legumes showed nitrogenase activity.Trema cannabina seedlings inoculated with Parasponia-Rhizobium invariably did not produce root nodules. The feasibility of Parasponia to accept foreign rhizobia bacteria or to produce pseudo-nodulation is probably genetically determined. In a karyological study it was shown thatParasponia parviflora had the chromosome number 2n=20.